WASHINGTON — The Obama administration has delivered a warning to Beijing about the presence of Chinese government agents operating secretly in the United States to pressure prominent expatriates — some wanted in China on charges of corruption — to return home immediately, according to American officials.

The American officials said that Chinese law enforcement agents covertly in this country are part of Beijing’s global campaign to hunt down and repatriate Chinese fugitives and, in some cases, recover allegedly ill-gotten gains.

The Chinese government has officially named the effort Operation Fox Hunt.

The American warning, which was delivered to Chinese officials in recent weeks and demanded a halt to the activities, reflects escalating anger in Washington about intimidation tactics used by the agents. And it comes at a time of growing tension between Washington and Beijing on a number of issues: from the computer theft of millions of government personnel files that American officials suspect was directed by China, to China’s crackdown on civil liberties, to the devaluation of its currency.

Those tensions are expected to complicate the state visit to Washington next month by Xi Jinping, the Chinese president.

The work of the agents is a departure from the routine practice of secret government intelligence gathering that the United States and China have carried out on each other’s soil for decades. The Central Intelligence Agency has a cadre of spies in China, just as China has long deployed its own intelligence operatives into the United States to steal political, economic, military and industrial secrets.

In this case, said American officials, who discussed details of the operation only on the condition of anonymity because of the tense diplomacy surrounding the issue, the Chinese agents are undercover operatives with the Ministry of Public Security, China’s law enforcement branch charged with carrying out Operation Fox Hunt.

The campaign, a central element of Mr. Xi’s wider battle against corruption, has proved popular with the Chinese public. Since 2014, according to the Ministry of Public Security, more than 930 suspects have been repatriated, including more than 70 who have returned this year voluntarily, the ministry’s website reported in June. According to Chinese media accounts, teams of agents have been dispatched around the globe.

American officials said they had solid evidence that the Chinese agents — who are not in the United States on acknowledged government business, and most likely are entering on tourist or trade visas — use various strong-arm tactics to get fugitives to return. The harassment, which has included threats against family members in China, has intensified recently, officials said.

The officials declined to provide specific evidence of the activities of the agents.

The United States has its own history of sending operatives undercover to other nations — sometimes under orders to kidnap or kill. In the years after the Sept. 11, 2001, attacks, the C.I.A. dispatched teams abroad to snatch Qaeda suspects and spirit them either to secret C.I.A prisons or hand them over to other governments for interrogation.

Neither China’s Ministry of Public Security nor the Ministry of Foreign Affairs responded to faxes requesting comment. But Chinese officials have often boasted about their global efforts to hunt economic fugitives, and the state news media has featured reports detailing the aims and successes of Operation Fox Hunt.

According to the Chinese news media, Beijing has sent scores of security agents abroad to “persuade” their targets to return home. Just how they accomplish their aims is unclear, and questions have been raised about why a number of suspects, presumably sitting on significant wealth abroad, have willingly returned to China.

Liu Dong, a director of Operation Fox Hunt, has said Chinese agents must comply with local laws abroad and that they depend on cooperation with the police in other countries, according to a news report last year. But in a telling admission, he added, “Our principle is thus: Whether or not there is an agreement in place, as long as there is information that there is a criminal suspect, we will chase them over there, we will take our work to them, anywhere.”

It is unclear whether the F.B.I. or the Department of Homeland Security has advocated within the Obama administration to have the Chinese agents expelled from the country, but the White House decision to have the State Department issue a warning to the Chinese government about the activities could be one initial step in the process.

The F.B.I. and the Department of Homeland Security are in charge of tracking the activities of foreign government agents inside the United States, and American officials said that both agencies had amassed evidence about the Chinese law enforcement agents by speaking to Chinese expatriates and by monitoring the agents themselves.

One American official acknowledged that Chinese agents had been trying to track down Ling Wancheng, a wealthy and politically connected businessman who fled to the United States last year and had been living in a lavish home he owns outside Sacramento. Should he seek political asylum, he could become one of the most damaging defectors in the history of the People’s Republic.

Chinese state news media published Interpol alerts in April for 100 people that Beijing described as its most-wanted fugitives worldwide. But experts who have studied the names raised doubts whether the listed men and women are truly the government’s top priority. Among the alleged fugitives, they said, are a former deputy mayor, employees of state-owned enterprises and a history professor, but few if any at the highest echelons of power.

American officials did not disclose the identities or numbers of those being sought by the Chinese in the United States. They are believed to be prominent expatriates, some sought for economic corruption and some for what the Chinese consider political crimes.

That reluctance reflects divisions with the Obama administration over how aggressive to publicly confront China on a number of security issues.

For instance, the White House has gone out of its way to avoid making any public accusations that the Chinese government ordered the computer attack on the Office of Personnel Management, which led to the theft of millions of classified personnel files of government workers and contractors. While James R. Clapper Jr., the director of national intelligence, initially said that “you have to kind of salute the Chinese for what they did,” he avoided repeating that accusation when pressed again in public on the matter.

China and the United States do not have an extradition treaty, and State Department officials would not say whether the warning carried any threats of penalties. Mark Toner, a State Department spokesman, declined to comment about the diplomatic warning but said that “generally speaking, foreign law enforcement agents are not permitted to operate within the United States without prior notification to the attorney general.”

It is a criminal offense, he said, “for an individual, other than a diplomatic or consular officer or attaché, to act in the United States as an agent of a foreign power without prior notification to the attorney general.”

Marc Raimondi, a spokesman for the Justice Department, said that “the United States is not a safe haven for fugitives from any nation.” But he added that if the United States was going to help China hunt down fugitives, Beijing must provide evidence to the Department of Justice.

Too often, he said, “China has not provided the evidence we have requested.”

Steve Tsang, a senior fellow at the University of Nottingham’s China Policy Institute, said the clandestine deployment of security agents in pursuit of Chinese abroad has a long pedigree under the Communist Party, which sees itself as wielding dominion over all Chinese people regardless of what passport they may hold. “The party believes if you’re of Chinese ancestry then you’re Chinese anyway, and if you don’t behave like one you’re a traitor,” he said.

Mr. Tsang said the agents’ methods of persuasion often relate to the person’s family back in China, ranging from subtle insinuations to explicit threats, including against children or grandchildren. “They can be very imaginative,” he said.

The agents are described as mostly young, highly skilled officers who have repeatedly undergone “rapid-fire deployment” since the campaign began last year.

“Within 49 hours, they can make their arrest anywhere in the world,” said a report published last year on Chinese Police Net, a website run by the Ministry of Public Security.

Such official statements, while directed toward a domestic audience, have stirred concern overseas. That is because Chinese agents are barred from making arrests on foreign soil, including the top destinations for alleged fugitives: the United States, Canada, Australia and New Zealand. These and a number of other countries do not have extradition treaties with China.

China says it follows local laws overseas. But in December, two Chinese police officers were caught operating in Australia without the permission of local authorities, according to local news media reports that were confirmed by Australian officials. The officers had traveled to Melbourne from the northeast province of Shandong to pursue a Chinese citizen accused of bribery, the reports said.

Australian officials promptly summoned diplomats from the Chinese Embassy in Canberra, as well as in Beijing, to express their displeasure, according to a spokesman for Australia’s Department of Foreign Affairs and Trade.

“The government registered with China its deep concerns about this, making clear it was unacceptable,” said the spokesman, who added “the government has been assured by Chinese authorities that there would be no repeat of these actions.”

Li Gongjing, a captain in the economic crime division of the Shanghai Public Security Bureau, explained the agents’ approach in an interview with Xinmin Weekly magazine last November.

“A fugitive is like a flying kite,” he said. “Even though he is abroad, the string is held in China. He can always be found through his family.”

Correction:

An earlier version of a capsule summary with this article rendered incorrectly the official name of the Chinese effort that uses covert agents in the United States to pressure expatriates to return home. It is Operation Fox Hunt, not Operation Fox.

Mark Mazzetti reported from Washington, and Dan Levin from Beijing.

A version of this article appears in print on , on Page A1 of the New York edition with the headline: China Is Warned Over Its Agents on American Soil. Order Reprints | Today’s Paper | Subscribe